City Visions for July 21, 2014: According to researchers, there are 100 trillion microorganisms living in the human body. But where does this 'human microbiome' come from? What do these microorganisms do for us and how are they related to chronic disease? And how can we keep our microbiome healthy?

City Visions host David Onek explores these questions and more with Bay Area leading researchers Katie Pollard of the Gladstone Institutes, Susan Lynch of UCSF, and Peter diLaura of Second Genome.